Nano-tribology and nano-mechanics are required in establishment of fundamental concepts of contact phenomena in small-scale and micro and nano-structures. In other hands, friction and wear of these components substantially depend on surface interactions which make their study difficult. As using nanoparticles in different applications has increased due to technology and material science improvements, nanoparticles behavior under different conditions has shown to be vital. One of these functions is using nanoparticles to decrease wear and friction in lubrication systems. The present research addresses the effect of adding nanoparticles on surface lubrication quality in theory and experiment. Moreover, several experiments are implemented in verifying the results. In theory, line contact problem between a semi-cylindrical pin and a flat surface disk in the presence of lubricant is numerically modeled. The pressure profile and film thickness are calculated and used to calculate the coefficient of friction. Then, the effect of nanoparticles as additives which carry part of the normal load is taken into account. Therefore, the total applied load is carried by asperities, fluid film and nanoparticles. In experiments, nano-lubricant of engine-oil and cupper-oxide (CuO) are used as lubricant in pin-on-disk test. After validation of theoretical results with experiments, the effect of nanoparticles weight fraction, load and speed are studied. Numerical results showed good agreement with experiments. The maximum error is 23 percent while the least error between numerical and experimental results was found for the case when 80 N load is applied. Keywords: Elastohydrodynamic equation, Line contact, Film thickness, Asperity load ratio, Nano-lubricant